The holy grail of alternative energy is practical, affordable energy storage. Without this, wind and solar energy can only be a partial solution to replacing fossil fuel energy. There is a growing awareness of the significance of this problem and a wide variety of technologies are gaining increased investment. However, the problem is hard and no technology as yet seems in sight of being both practical and affordable. The goal is $100/kWh, and/or $1/W with long life and high round trip efficiency. Most technologies exceed $500/kWh and have problems with life, efficiency and/or geography. The StratoSolar main page lists some companies trying new storage approaches in the 'related sites' list on the right. StratoSolar PV electricity solved cost, reliability and geographic independence problems of Solar PV, but it still did not produce energy at night, and has been dependent on the eventual emergence of a viable energy storage technology. Over recent months we have made a very significant breakthrough in energy storage technology intimately tied to the StratoSolar solution. This new invention makes StratoSolar PV power plants complete 24/7 producers of electricity. The new StratoSolar technology is a variant of gravity energy storage. The most common electricity energy storage method is pumped hydroelectric, which is a form of gravity energy storage. This pumps a mass of water from a low reservoir to a high reservoir, storing energy as gravitational potential energy. Gravitational potential energy is mass times height times gravitational acceleration. For pumped hydroelectric storage, the height is small, measured in hundreds of meters and the mass is large. Measured in tens of thousands of tonnes. StratoSolar gravity energy storage instead makes use of the great height of platforms to store energy with relatively small masses. The height is about 20,000 meters, but the masses are measured in hundreds of tonnes. Winches raise the masses to store energy and lower them to recover energy. Each kg of mass can store about 54Wh of gravitational potential energy. Stored energy can scale with generated PV electricity. Each square meter of PV panel can generate about .9kWh/day to 1.3kWh/day, depending on latitude and gravity energy storage can easily store about 300Wh to 500Wh for each square meter. This balance of generation and storage allows a 24/7 electricity supply with the ability to respond to changing demand more quickly than expensive 'peaking generators'. This approach costs about $125/kWh today but with volume can scale to much lower cost. It also has a long life, high reliability and high round trip efficiency. So StratoSolar now provides a complete 24/7 replacement for fossil fuel electricity generation at lower cost and zero CO2 emissions.